Processed wastes as supplemental fuel for modified cement films

ABSTRACT

A method is described for environmentally sound usage of combustible hazardous waste in an operating rotary kiln. The method is particularly adapted for disposal of solid hazardous wastes, optionally in the form of a blended waste homogenate, packaged in sealable containers. The containers are used as fuel modules and charged into a rotary kiln cylinder where kiln gas temperatures range from about 950° to about 1200° C. to achieve high destruction and removal efficiencies.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending U.S. Pat. application Ser.No. 07/613,238, filed Nov. 9, 1990, now U.S. Pat. No. 5,058,513 whichwas a continuation of U.S. Pat. application Ser. No. 07/412,287, filedSept. 25, 1989, now U.S. Pat. No. 4,974,529, which was a continuation ofU.S. Pat. application Ser. No. 07/347,075, filed May 16, 1989,abandoned, which was a division of U.S. Pat. application Ser. No.07/275,402, filed Nov. 23, 1988, now U.S. Pat. No. 4,852,290.

FIELD OF THE INVENTION

The present invention relates to use of hazardous wastes in rotarykilns. More particularly, this invention is directed to a method foraccomplishing environmentally sound disposal of hazardous wastescomprising combustible waste solids and to recover their availableenergy values in mineral processing kilns.

BACKGROUND AND SUMMARY OF THE INVENTION

Solid combustible wastes have always been generated by industry. Many ofsuch wastes, because of their flammable or toxic character, arecategorized by applicable environmental regulations as "hazardouswastes". Prior to governmental regulation of the disposal of suchmaterials, they were disposed of by dumping in landfill operations.Significant environmental damage has been caused by those practices.With recently enacted environmental regulations imposing severerestrictions on landfill-type disposal of hazardous wastes, the onlyviable means for their safe disposal has been by thermal treatment,typically at high cost in specialized hazardous waste incineratorsequipped with extensive emission control devices.

Cement kilns have received favorable review from both federal and stateenvironmental regulatory agencies as providing ideal conditions fordisposal of combustible waste materials. Not only does the burning ofhazardous waste in operating kilns allow recovery of energy values fromhazardous wastes, but also, because of their high operatingtemperatures, long residence times and their ability to providefavorable conditions for the chemical combination of inorganic residuesinto the active compounds of portland cement, such operations provideideal conditions for environmentally sound disposal of combustiblehazardous waste materials.

However, because of problems unique to the handling and burning of solidhazardous waste in operating kilns, regulation compliant disposal ofhazardous wastes in operating kilns has been limited to combustibleliquid or "pumpable" hazardous waste. Liquid waste materials are easilyblended with each other and with conventional fuels to providehomogeneous liquids that can be burned in the gaseous phase at thefiring end of the kiln with little or no modification of kiln burnerconfiguration. Solid hazardous wastes, however, can occur in amultiplicity of forms, from hard crystalline solids to viscous, stickysludges. They are not easily blended and they present significantengineering challenges for their safe handling and delivery into rotarykilns. Further, the burning of combustible solids in the firing chamberof a kiln faces other practical problems. Hazardous waste solids are noteasily dispersed into the flame of the burning primary fuel. If waste,solids are charged into the primary combustion zone, they willnecessarily come into contact with the mineral bed at a very criticaltime in the clinker-forming process It is important for the formation ofquality clinker, both in terms of color and performance, that oxidizingconditions be maintained in the clinker-forming zone of the kiln.Charging combustible solids onto the forming clinker at temperatures inexcess of 1300° C. can create reducing conditions in the forming clinkerand adversely affect cement quality.

Before promulgation of existing EPA air quality regulations, it was apractice to charge combustible solid waste into the cold end of the kilnwith the to-be-processed mineral materials. Such practices continue incountries where emission standards are not in effect or not enforced.Today, however, without added expensive emission control equipment,combustible solid hazardous waste cannot be charged to the cold end ofthe kiln and still allow the kiln to operate in compliance withenvironmental regulations controlling kiln emissions. Combustible solidhazardous waste by definition can contain a wide range of volatileorganic substances. Combustible hazardous waste solids, added with theraw material to the "cold" or upper end of a conventional kiln, withoutcombustion gas afterburners or other emission control equipment, resultsin unacceptable levels of hydrocarbon emissions. As the raw material andwaste solids move down the kiln cylinder to higher and highertemperature zones, volatile components are driven off into the effluentgases at temperatures below those required for thermal degradation ofthe volatilized components. The result is discharge of a significantamount of the volatile compounds into the atmosphere. Particulateresidue fuels with low volatiles content can be added either to themineral material introduced at the cold end of the kiln or to thecalcining zone with efficient energy value usage and apparently withoutnotable problems with hydrocarbon emission levels. See, for example,U.S. Pat. No. 4,022,629 and references cited therein.

Combustible hazardous waste solids represent a significant potentialsource of inexpensive energy to the energy intensive mineral processingindustry. However, concerns about waste handling, plant engineering,end-product quality and emission control has deterred kiln operatorsfrom taking advantage of the inexpensive energy values available throughburning of hazardous waste solids. That has been true particularly inview of the availability of, and the environmentally sanctioned use of,hazardous waste liquids as inexpensive alternate fuels for kilnoperations. However, with the promulgation of environmental regulationsimposing severe restrictions on land disposal of solid hazardous wastes,and the limited availability (and high costs) of EPA-approved completecombustion facilities, there has been a significant effort directedtoward the development of alternate means for safe disposal of solidhazardous wastes. The present invention evolved from that effort.

One object of this invention is to provide a safe, environmentallyacceptable method for disposal of hazardous waste materials, includingparticularly hazardous waste solids, which contain significant levels ofcombustible and/or toxic organic compounds and toxic inorganicsubstances. It is another object of this invention to provide a methodof recovering energy values of solid combustible hazardous wastematerials and of using such materials to provide up to 40% or more ofthe energy requirements of kiln operation. The method is fully compliantwith applicable environmental emission regulations, and it also allowsfor the most efficient use of the waste material as fuel in the processwithout compromising quality of the processed mineral product.

One aspect of the invention comprises a unique configuration ofhazardous waste processing, packaging (containerization), and kilncharging techniques which enables kilns to use controlled quantities ofhazardous wastes as supplemental fuel while maintaining compliance withenvironmental emission standards and minimizing the risk of personalinjury to individuals handling of the waste products.

This has been practiced by preparing fuel modules of containerizedhazardous wastes. Most preferably the hazardous waste is packaged inportions having energy values within a predetermined energy value range.The fuel modules are charged into an operating kiln at a point where thetemperature and process conditions assure environmentally sound disposalof both volatile and non-volatile waste components and where energy andmaterial content of the waste material most efficiently contribute tothe mineral processing operation. Containers of the combustiblehazardous waste are charged to the kiln at regular intervals at a pointin the kiln where kiln gas temperatures range from about 950 to about1200° C., more preferably from about 950° C. to about 1100° C. Thesetemperatures are high enough to assure complete combustion ofvolatilized components but not so high that where the process isconducted in a mineral processing kiln, the presence of the combustiblenon-volatile portion of the charged waste in the mineral bed createsconditions detrimental to product quality.

One embodiment of the invention is an apparatus that enables thecharging of solid fuel or containerized fuel through the wall of arotating kiln cylinder. A port, preferably with a mechanical closure inthe kiln cylinder wall is aligned with a drop tube inside the kilncylinder. The drop tube prevents hot mineral material in the kiln fromescaping through the port or contacting the closure. Fuel is deliveredto the kiln through the port and the drop tube at predetermined timesduring kiln cylinder rotation.

Blending hazardous waste material to form hazardous waste homogenatesprior to containerization facilitates process control and minimizesperturbation of kiln operation Conditions by assuring some uniformity(from container to container) in terms of waste composition, form,energy value and combustion characteristics. Containerization of thehazardous waste, preferably as a hazardous waste homogenate, not onlyprovides a safe and convenient means for handling and shipping ofhazardous wastes, but it also seems to play an important role in thesatisfactory degradation of the contained waste, particularly thevolatile portion, in the kiln. Sealed containers of hazardous wastes arecharged into the kiln at a point where kiln gas temperatures are highenough to decompose or complete combust volatile components driven intothe gas stream. It is important that the volume of volatile componentsnot exceed the capacity for their complete combustion in the gas stream.With the hazardous waste in sealed containers or modules, release of thevolatile components of the contained hazardous waste into the kiln gasstream occurs over a period of time commensurate with the time formelting or disintegration of the container itself. Containerization ofthe waste therefore minimizes the potential for overloading the completecombustion capacity of the kiln gas stream with volatile organics. Theresult is a destruction and removal efficiency (DRE) of principalorganic hazardous constituents (POHC's) of 99.99% and higher for theprocess.

Introduction of the containerized waste in the 950-1200° zone of thekiln not only assures acceptable complete combustion of volatilecomponents but also enables efficient use and disposal of thenon-volatile components. Combustible non-volatile components are burnedwhile in contact with the calcining mineral material allowing for highheat transfer efficiency. The inorganic components of the non-volatileresidue come into immediate contact with and react chemically with thefree calcium oxide forming in the mineral bed to become incorporatedinto the cement materials and rendered non-hazardous.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a conventional rotary kilnequipped with the present fuel charging apparatus.

FIG. 2 is a cross-sectional view of the kiln cylinder taken along theline 2--2 of FIG. 1.

FIG. 3 is a cross-sectional view taken along line 2--2 the kiln cylinderin FIG. 1 rotated about 90°.

FIG. 4. is a cross-sectional view of the fuel charging apparatus takenalong the line 4--4 in FIG. 3.

FIG. 5. is similar to FIG. 2 illustrating an alternate embodiment of thecharging apparatus.

FIG. 6. is a partial cross-sectional view of the apparatus shown in FIG.5 with the kiln cylinder rotated about 30°.

FIG. 7 is a partial cross-sectional view of the upper end of apreheater/precalciner type kiln modified to carry out the inventiveprocess.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

This invention relates to a method for achieving environmentally sounddisposal of combustible hazardous waste in an operating rotary kiln.Rotary kilns can be of the conventional type or of the so-calledpreheater or precalciner type. Common to each, however, is a heated,rotating cylinder containing in-process mineral material In the widelyused commercial process for the production of cement clinker, cement rawmaterials are calcined and "clinkered" by passing finely divided rawmaterials through a rotating inclined rotary kiln or kiln cylinder. Therequisite temperatures for processing the mineral material are achievedby burning fuel such as gas, fuel oil, powdered coal and the like in thegaseous atmosphere at the lower end of the kiln with the gases movingcountercurrent to the solids through the rotating kiln cylinder. Withthe high temperatures required for the process, fuel costs constitute asignificant factor in the ultimate cost of the product. Presently fuelcosts are often reduced, through burning of pumpable liquid hazardouswastes, alone or in combination with conventional fuels.

In what is known as long dry or wet process kilns the entire mineralheating process is conducted in the rotating kiln cylinder. The cylinderis typically 10 to 12 feet or more in diameter and 300-500 feet inlength and is inclined so that as the cylinder is rotated, raw materialsfed into the upper end of the kiln cylinder move toward the lower"fired" end where the final clinkering process takes place and theproduct clinker is discharged for cooling and subsequent processing.Temperatures in the fired clinkering zone of the kiln range from about1300° C. to about 1600° C. Gas temperature in the kiln decreases to aslow as about 150°-200° C. at the upper mineral material receiving end ofso-called wet process kilns. Somewhat higher gas temperatures exist inthe upper end of dry process kilns.

Preheater or precalciner kilns have, in addition to the inclinedrotating kiln cylinder fired at the lower discharge end, an apparatusfor preheating or precalcining the mineral material before it is chargedinto the upper end of the rotating kiln cylinder. The kiln is typicallymuch shorter than kiln cylinders in conventional long dry and wetprocess kilns. The gas temperatures inside the rotating kiln cylinder ofa precalciner type kiln ranges from about 1300° to about 1600° C. at thefired discharge end to about 950-1200° C. at its uppermost end.

In the present method, combustible hazardous waste, preferablycombustible hazardous waste solids, are containerized and charged intothe kiln to contact the mineral material at a point along the length ofthe kiln cylinder where the kiln gas temperatures ranges from about 950°C. to about 1200° C. In a conventional long dry and wet process rotarykiln, that range of gas temperatures is typically found in the kilncylinder in a zone that corresponds approximately to the middle axialone-third portion of the kiln cylinder. In a preheater or precalcinertype rotary kiln, the specified gas temperature ranges exist in aboutthe upper one-third portion of the rotary kiln cylinder.

Hazardous wastes which can be charged to a kiln for disposal inaccordance with this invention typically have volatile components, whichare volatilized from the waste material as it contacts the hot mineralmaterial, and non-volatile components comprising both combustible highmolecular weight organic materials and non-combustible inorganicmaterials. It is critical to the environmental integrity of the presentprocess that the volatile components entering the kiln gases aredestroyed or complete combusted before being discharged from the kiln.Complete combustion of the volatile components is a function of gastemperature, residence time, and oxygen content. Thus, incompletecombustion evidenced by high hydrocarbon emissions or high carbonmonoxide levels in the waste gas stream, could mean that the gastemperature at the point of complete combustion is too low, that therewas insufficient oxygen to complete combustion either because of lowkiln gas oxygen or because of unusually high volatile concentration, orinsufficient residence time. It has been found that under normal kilnoperating conditions where the hazardous waste is containerized andcharged into the kiln where kiln gas temperatures are in a range fromabout 950° to about 1200° C., the process can be conducted consistentlyand continuously with a DRE of POHC's at 99.99% and higher.

Hazardous waste destruction efficiency of the process can be monitoredas a function of carbon monoxide and/or total hydrocarbons in theeffluent gas stream. Each kiln modified to carry out the present processcan be calibrated, for example during a test burn of containerized solidhazardous waste, so that carbon monoxide concentration in exhaust gasescan be utilized as a direct indication of the DRE of the ongoingprocess. Thus, for example, carbon monoxide concentration ranging fromabout 100-2000 parts per million can be determined to correspond to adefined range of hydrocarbon emissions. Continuous monitoring ofeffluent gases assures full compliance with applicable environmentalregulations and consistent product quality.

"Environmentally sound disposal" as used in the description of theinvention means disposal of the hazardous waste with a destruction andremoval efficiency of principal organic hazardous constituents of atleast 99.99% and correspondingly minimal emissions of other possibleenvironmental contaminants. The hazardous waste materials that can beprocessed in accordance with this invention can be derived from a widevariety of industrial sources and can assume an equally wide range offorms and chemical composition. They can be in the form of hard solids,sludges, viscous tar-like residues, and often consist of high molecularweight organic resins. The term "hazardous waste is intended to refer tothose waste products designated as hazardous under applicableenvironmental regulations, particularly those that are so categorizedbecause of their inherent toxicity and/or flammability or their contentof toxic and/or flammable materials. While the process is particularlyadapted to destruction of combustible hazardous waste solids, volatileconstituents of typical solids are readily tolerated and safely andeffectively complete combusted in the process.

It is contemplated that this process finds application, too, for thermaltreatment of soils contaminated with toxic and/or combustible hazardouscompounds.

The hazardous waste materials are containerized for safe shipment andhandling and for complete combustion control of volatile constituents inthe process. Further, to facilitate control of kiln operatingconditions, it is preferred that hazardous waste materials for use inthe process be collected, optionally categorized so that hard solids canbe comminuted and blended with other hazardous waste materials to form ahazardous waste homogenate. Individual lots of hazardous wastehomogenates can also be categorized in terms of ash content, volatiles,halogen content and energy value per unit weight. Portions of the wastehomogenate are then packaged into sealed containers adapted to becharged into a rotary kiln in accordance with the present disposalprocess utilizing, for example, the charging apparatus illustrated inFIGS. 1-4. Each container is filled to contain an amount of hazardouswaste or hazardous waste homogenate so that each container has an energyvalue within a predetermined energy value range and then sealed. Thus, aspecific example was a 1000-container lot of "fuel modules" for use inthis invention that had an energy value (heat of combustion), includingthat of the container itself, of 300,000 to 500,000 BTU. The resultingcontainer-to-container consistency in combustion properties and energyvalues facilitated process control for production of a mineral productwithin specifications and promoted the maintenance of kiln operatingconditions appropriate for environmentally sound disposal of thehazardous waste materials charged into the process.

One form of hazardous waste which has been successfully utilized in thisprocess is a by-product of the production of liquid waste fuels alreadymarketed by Cadence Chemical Resources under the name CHEM FUEL® forburning in kiln operations. The solid hazardous waste by-productsconsist of the non-volatile and non-extractable residues which consistprincipally of high molecular weight resins, polymers and residualvolatiles. Preferably the hazardous waste containerized for use in thepresent process should have a BTU value of greater than 5,000 BTU/lb.Free liquids in the solid waste materials should be minimized. Ifpresent, they may be absorbed using an organic absorbent material suchas ground corncobs or similar BTU contributing material.

Sealable containers for the hazardous waste should be fully compliantwith applicable Department of Transportation standards forcontainment/shipment of hazardous waste materials. Sealable steel pailsor drums are preferred. The container contributes both energy (iron isoxidized in the higher temperature zones near the discharge end of thekiln) and material (iron oxides) to the process chemistry. Othercontainers such as fiber and plastic may also be used. The size of thecontainers are dependent on the energy value of the hazardous wastetargeted for disposal and the capacity of the kiln to receive suchcontainers.

In a representative embodiment of the invention a homogenate ofhazardous waste solids having a minimum energy value (heat ofcombustion) of 6,000 BTU/lb, a chlorine content of less than 6.66% andPCB's at less than 50 ppm is packaged in six-gallon steel pailsconforming to DOT Specification 17H or 37A. The pails are open headcontainers with sealable lug-type covers. The pails are 26 gauge steelbodies and lids for net contents of less than 60 lbs. and 24 gauge steelbodies and lids where the net weight of the contents is greater than 60lbs. and less than 80 lbs. The combustible waste material is filled intothe pails which are then sealed and the gross weight of each pail ismarked on the lid. Each pail is then marked with the necessary labelsand markings to conform with DOT, state and other regulations. It isdesirable that the homogeneity of the hazardous waste material be suchthat there not be more than 3,000 BTU/lb difference between containersin any given lot of containers.

Performance of the present method for achieving environmentally sounddisposal of combustible hazardous waste in conventional long dry and wetprocess kilns is achieved by a novel charging apparatus comprising aport in the wall of the kiln cylinder, a drop tube extending from theport into the kiln cylinder and positioned so that the mineral materialin the kiln will not pass through the port or contact the port closureduring rotation of the kiln cylinder, means for receiving the fuel andpositioning same for passage through the port, and means for applying aforce to said containerized fuel sufficient to move the fuel from thereceiving and positioning means through the port and drop tube and intothe kiln cylinder. Preferably a closure is provided for the port alongwith means for actuating the closure to open and close the port atpredetermined times during rotation of the kiln cylinder.

FIG. 1 illustrates a conventional long dry and/or wet process kiln 10having kiln cylinder 12 with lower fired end 14 where processed mineralmaterial 16 is discharged from cylinder 12. Mineral material is chargedto the upper end 20 of kiln cylinder 12 and moves down kiln cylinder 12as it is rotated about its axis at a rate of about 1 to about 3 timesper minute. Exhaust gases from kiln 10 may be treated to removeparticulates at emission control station 22 utilizing bag filters orelectrostatic precipitators (not shown). The flow of gases through kilncylinder 12 is controlled by blowers 24 which direct the exhaust gasesthrough stack 26. A solid fuel charging apparatus 28 is located atapproximately the mid-point of kiln cylinder 12.

Fuel modules 30 are located on elevated platform 32 from which they areloaded into charging apparatus 28 as the kiln cylinder 12 rotates. Athermocouple 33 is located about 10 to about 50 feet downstream (uphill)from charging apparatus 28 to monitor gas temperature in kiln cylinder12.

Referring to FIG. 2, charging apparatus 28 consists of drop tube 34extending into the kiln cylinder a distance greater than the maximumdepth of mineral bed 36. Drop tube 34 communicates with port 38 in wall40 of kiln cylinder 12. Port 38 also communicates with fuel receivingchute 42. Fuel receiving chute 42 is designed so that when fuel module30 is received in chute 42, fuel module 30 is positioned in alignmentwith port 38.

With reference to FIGS. 2 and 3, closure 44 is provided for port 38.Pivoted lever 46 is provided for actuating closure 44 between aport-opened position (FIG. 3) and a port-closed position (FIG. 2).Closure 44 is biased in the closed position by spring 48 cooperatingwith lever 46. Lever 46 is positioned so that as kiln cylinder 12rotates to a point where port 38 is near its highest position duringrotation of kiln cylinder 12, lever 46 contacts fixed cam 50 through apredetermined arc of rotation of kiln cylinder 12 to move lever 46 fromthe biased port-closed position to the port-opened position so that fuelmodule 30 falls with force of gravity from receiving chute 42 throughport 38 and drop tube 34 and onto mineral bed 36 As the kiln cylinder 12is rotated past the position where the fuel module 30 is transferredinto the kiln cylinder, lever 46 moves past cam 50 and the closurereturns to its biased port-closed position. Cam 50 is positioned on cammount 52 which can be moved from an apparatus-operating position (shownin FIG. 5) to a position where cam 50 does not contact lever 46 duringrotation of kiln cylinder 12.

Closure 44 is positioned relative to port 38 and sized so that when itis in the port-closed position, clearance is allowed for air flow intokiln cylinder 12 under the influence of negative pressure in kilncylinder 12 effected by blowers 24. Air flow through port 28 aroundclosure 44 and into kiln cylinder 12 through drop tube 34 helps to coolclosure 44 and drop tube 34. Air temperature in kiln cylinder 12 in thevicinity of drop tube 34 ranges from about 950° C. to about 1200° C.Drop tube 34 must be constructed of a material which can withstand thosethermally harsh conditions over long periods of time. It is preferablyconstructed of an alloy material protected by refractory 35. One alloyfound suitable for construction of the drop tube 34 is an alloy sold byDuralloy Blaw-Knox under the trademark SUPER 22-H.® That alloy is apatented high strength alloy designed for service to 2250° F. (pb 1230°C). Its stated chemical composition is as follows: nickel, 46-50%;carbon, 0.40-0.60%; chromium, 26.0-30.0 %; manganese, 1.50% max.;silicon, 1.75% max.; tungsten, 4.00-6.00%; molybdenum 0.50% max.;cobalt, 2.50-4.00%; sulfur, 0.04% max.; and phosphorus 0.04% max.

Sensor 56 is positioned to detect transfer of fuel module 30 throughport 38 and into kiln cylinder 12. An audible or visible signal isgenerated to indicate that the transfer is complete.

In operation, fuel module 30 is loaded from elevated platform 32 intokiln cylinder mounted fuel receiving chute 42 as it passes elevatedplatform 32. As kiln cylinder 12 is rotated and fuel receiving chute 42approaches a near vertical position, fixed cam 50 contacts pivoted lever46 moving closure to the port-opened position allowing fuel module 30 todrop through port 38 and drop tube 34 and onto mineral bed 36. As kilncylinder continues its rotation and pivoted lever 46 moves past fixedcam 50, the closure is returned to the port-closed position by action ofspring 48 on pivoted lever 46.

With reference to FIG. 5 there is illustrated a second embodiment of afuel module charging configuration. Drop tube 134 communicates with port138 and extends radially inwardly into the kiln cylinder. Fuel receivingchute 142 is stationary and mounted immediately above the rotating kilncylinder. Stationary fuel receiving chute 142 is positioned so that itcomes into alignment with port 138 and drop tube 134 once on eachrevolution of kiln cylinder 112. A fuel module retaining rail 60 ismounted circumferentially on the exterior of kiln cylinder 112 at anaxial position in alignment with both port 138 and stationary fuelreceiving chute 142 and having rail termini 62, 64 at opposite edges ofport 138 so that when fuel module 30 is positioned in receiving chute142 it rides on retaining rail 60 until rail terminus 62 of retainingrail 60 clears fuel module 30 at a point where receiving chute 142, port138 and drop tube 134 are in alignment, and fuel module 30 falls underthe force of gravity through port 138 and drop tube 134 onto the mineralbed as is shown in FIG. 6. Fuel module retaining rail 60 and port 138are enclosed in fixed annular housing 145 which helps to control airinfiltration into kiln cylinder 112 through port 138. As kiln cylinder112 rotates and rail terminus 64 clears the fuel receiving chute 142,the next fuel module can be transferred to receiving chute 142.

With reference to FIG. 7, fuel modules 30 can be delivered directly intothe mineral bed 236 in the upper end 220 of rotary kiln cylinder 212. Innormal operation, mineral material is preheated by the heat contained inthe exhaust gases. In precalciner operations, fuel is added to the riserduct 266 and combusts either with excess air in the kiln gas oradditional air provided through a separate duct 269. The energy releasedby this combustion is absorbed by the mineral material before enteringthe kiln. This preheated mineral material travels down a duct parallelto the fuel module delivery tube 270 and then down ramp 268 and intoupper end 220 of inclined rotating kiln cylinder 212 where thermalprocessing of the mineral material is completed as it moves downrotating kiln cylinder 212. A fuel, module delivery tube 270 isinstalled at the upper end of ramp 268 at the base ofpreheater/precalciner riser duct 266. Delivery tube 270 has a ceramiclined portion 272 proximal to the base of the riser duct 266 and isequipped with master gate valve 274 and upper and lower gate valves 276and 278, respectively, operated during the fuel module loadingprocedure. The delivery tube is configured so that a fuel moduleentering the base of riser duct 266 through delivery tube 270 hassufficient momentum to carry it quickly down ramp 268 and onto themineral bed 236 in upper end 220 of rotary kiln cylinder 212. Fuelmodules are charged into the kiln through delivery tube 270 atpredetermined intervals ranging from about 30 seconds to about 2 minutesusually one every 60 seconds.

In operation, a fuel module is delivered to the kiln by the followingprocedure. With lower gate valve 278 closed, upper gate valve 276 isopened and fuel module 30 is loaded into upper end 280 of delivery tube270. Upper gate valve 276 is closed and at the predetermined time, lowergate valve 278 is opened to allow fuel module 30 to fall down deliverytube 270 across ramp 268 and onto mineral bed 236.

It is contemplated that waste fuel modules could also be delivered intothe upper portion of the kiln cylinder of a precalciner type kilnutilizing, for example, the charging apparatus illustrated in FIGS. 2-4.The apparatus can be positioned at a point, along the upper one-thirdportion of the rotary kiln cylinder where the kiln gas temperaturesrange from about 950° to about 1200° C., more preferably between about950° C. and 1100° C.

Measurements of destruction and removal efficiency and particulateemissions has already been conducted on a precalciner rotary kiln havinga construction substantially as illustrated in FIG. 7. A test burn wasconducted in which 10% of the process energy came from solid hazardouswaste derived fuel introduced in steel containers onto the mineral bedin the upper end of the rotary kiln cylinder. The tests were conductedwith a specially prepared surrogate waste derived fuel spiked withchlorinated hydrocarbons. The containerized fuel was fed into theprocess at a rate of 3900 lbs/hr. The destruction and removal efficiencywas found to be well in excess of 99.99% in all tests.

Comparable results were obtained in a conventional long dry and wetprocess rotary kiln (12'×450') fired at the rate of 150-250 millionBTU's per hour of coal, gas or liquid hazardous waste derived fuel.During a test burn a specially prepared surrogate waste derived fuelenriched in paint pigments, to give maximum heavy metal input, andspiked with at least 5% trichlorobenzene was used. The principalcomponent of the solid waste was high molecular weight non-volatilepolymers and resins obtained as a by-product of the production of liquidhazardous waste derived fuel. The waste blend was packaged in 24 gaugesteel pails with sealable lug-type covers and were introduced to themid-point of the rotary kiln cylinder at a rate of one (1) container perminute. At 5% trichlorobenzene, the POHC input rate was about 3.25lbs/minute. During the test burn, the concentrations of carbon monoxide,nitrogen oxide, oxygen and sulfur dioxide in the exit gases weremonitored as well as mineral material feed rate, fuel rate, kiln speed,and gas temperatures at various points along the length of the kilncylinder. Throughout the test run, the gas temperature was monitored bya thermocouple 12 feet downstream (uphill) of the point of introductionof the waste fuel modules. This temperature was maintained above 925° C.at all times. preliminary data collected during the test burn predicts aDRE providing a high margin of safety for environmentally sounddestruction of solid hazardous waste.

What is claimed is:
 1. A method for achieving environmentally sounddisposal of solid waste having volatile components in an operatingrotary cement kiln comprising a heated, rotating cylinder containingin-process mineral material, said method comprising the steps ofprocessing said waste to retard the release of its volatile componentsand charging the processed waste into the kiln to contact the mineralmaterial at a point along the length of the kiln cylinder where the kilngas temperature is sufficient to decompose the volatile components ofthe waste.
 2. The process of claim 1 wherein the processed waste ischarged into the kiln through a port in the kiln cylinder wall locatedat a point where the processed waste charged into the kiln contactscalcining in-process material materials.
 3. The method of claim 1wherein the rotary kiln is a long dry or wet process rotary cement kilnfired at its discharge end and the processed waste is charged into thekiln cylinder at a point along the middle axial one-third portion of thekiln cylinder.
 4. The method of claim 3 wherein the processed waste ischarged through a port in the kiln cylinder wall.
 5. The method of claim1 wherein the operating rotary kiln is a preheater or precalciner typerotary kiln having a preheater portion upstream from a rotating kilncylinder having an upper end for receiving preheated mineral materialfrom the preheater portion and a fired lower end where mineral materialis discharged from the kiln, and wherein the processed waste is chargeddirectly into the upper end of the kiln cylinder.
 6. The method of claim5 wherein the processed waste is charged through a port in the kilncylinder wall.
 7. A long wet or dry process cement kiln comprisingrotary cylinder for containing and heat processing a mineral material toform cement clinker, said kiln modified for the environmentally sounduse of combustible solid wastes having volatile components as supplementfuel for the energy efficient production of cement clinker, saidmodified cement kiln further comprising a solid waste delivery port inthe rotary cylinder, said port located at a point along the axial lengthof the cylinder where during kiln operation the kiln gas temperature issufficient to decompose the volatile components of the solid waste. 8.The modified cement kiln of claim 7 wherein the solid waste deliveryport is located on the middle axial one-third portion of the cementkiln.
 9. The modified cement kiln of claim 7 wherein the solid wastedelivery port is located at a point along the axial length of thecylinder where during kiln operation the contained in-process mineralmaterial is in a calcining state.
 10. The modified cement kiln of claim7 wherein the port is provided with a closure movable between aport-opened and port-closed position.
 11. The modified cement kiln ofclaim 7 further comprising a drop tube communicating with the port andextending into the kiln cylinder a distance greater than the maximumdepth of the contained in-process mineral material.